Merge pull request #10 from kyleboon/master

Changed separator for task rules
Adding cache gradle task
Fixed bug caching templates that don't exist

If you give lazybones a template name that doens't exist in bintray,
it throws an exception that the URL doesn't exist but it creates a 0
byte file in the cache directory. If you try to run lazybones again for
that template, it will find it in the cache but the 0 byte file is an
invalid zip file.